Photophysical properties of multiply phenylated C70 derivatives:: Spectroscopic and quantum-chemical investigations

The photophysics of six multiply phenylated C-70 derivatives [C70Ph2, C70Ph4, C70Ph6 (two regioisomers), C70Ph8 and C70Ph10] have been investigated by means of steady state spectroscopy in cyclohexane solution and quantum-chemical calculations derived from semiempirical Hartree-Fock approaches. There is good agreement between the measured absorption spectra and the INDO/SCI calculated excitation energies for each derivative. The foregoing results and some additional ground state properties calculated at the AM1 level have been used to predict that the perturbation of the pi electronic system of the cage results in significant changes in the photophysics of the fullerene derivatives. The effects of conjugation and spatial localization of the HOMO and LUMO orbitals on the energy of the first electronic transition are discussed in greater detail. (C) 2000 American Institute of Physics. [S0021-9606(00)00113-6].